Muzzle loading rifles have an essentially closed breech at the rear of the barrel, so that powder and projectiles must be loaded at the muzzle or forward end of the barrel. A typical muzzle loading rifle has a barrel with a breech plug attached to occupy an enlarged, internally threaded, rear bore portion of the barrel at the breech end. In some rifles, the breech plug is permanently attached. In others, the breech plug is removable to facilitate pass-through cleaning of the bore or similar operations.
A conventional removable breech plug employs a finely threaded elongated body that screws into the rear of the barrel, which is internally threaded to receive the plug. Typically, ten to fifteen turns are required to secure the breech plug in place. The breech plug is not removed for normal loading operations, but rather for cleaning purposes. The cleaning process involves removing the breech plug, and then passing a brush-tipped rod through the entire length of the barrel by inserting the rod into one end of the barrel and dragging it out of the other end. The brush, wetted with a liquid cleaning agent, dissolves and dislodges fouling.
During a typical shooting session, the breech plug remains closed. For each shot, powder and a projectile are inserted into the muzzle, and a fresh primer is inserted into a pocket that is centrally located at the rear of the breech plug. When the firearm is discharged, the primer is ignited and a small-diameter passage in the breech plug transmits the flash from the primer to the powder in the barrel interior. The primer is retained in place by a breech block that swings into a locked position over the breech plug, and the primer may be removed when the breech block is moved away to an unlocked position. Such a system is shown in U.S. Pat. No. 6,604,311 entitled “Lever Operated Breechblock for Muzzle-Loading Firearm,” which is incorporated herein by reference. This system utilizes a fixed barrel and stock, and a drop down-type firing mechanism and breech block assembly. The firing mechanism and breech block are pivotally attached to the barrel/stock through a linkage that is operated by a lever on the trigger guard. In a closed position, the breech block is locked over the breech plug, and the firing mechanism is located in a conventional position for firing, with the trigger lying proximate to the underside of the stock. For opening the assembly, the lever on the trigger guard is pulled downwards, causing the entire firing mechanism and breech block assembly to pivot downwards.
Although the system in U.S. Pat. No. 6,604,311 is functional, it includes a stock that is fixed to the barrel. This makes it more difficult for pass-through cleaning, since the upper portion of the stock, located to the rear of the breech, limits access to the breech. To provide unlimited access, the stock must be contoured to provide an access space, which may disadvantageously limit design options. Furthermore, the stock portion adjacent to the breech may make it more difficult or slow to insert a new primer, and to access the breech for breech plug removal. Additionally, because the major components (e.g., stock and barrel) of the rifle are fixed with respect to each other, it requires more scrutiny to determine whether the rifle is in a clearly inoperable condition. For example, when lying with the breech block moved to the open position (preventing the firing pin from striking the primer), the position of the trigger guard is not readily detected at a distance, such as might be desired at a shooting range, during instruction, or a similar situation.
A further limitation of existing designs is that the process required for cleaning is somewhat cumbersome. In the system of U.S. Pat. No. 6,604,311, for example, to clean the barrel without a risk of harming the stock with cleaning solution, the stock must be removed. This requires removal of a butt pad from the stock, and the rear stock from the rifle by removing a blind screw. This can be somewhat difficult for the user, and risks damage. Moreover, the receiver and other operational elements remain attached to the barrel, making cleaning less convenient.